1. Field of the Invention
The embodiments of the present invention relate to a thin film transistor (TFT) and a method of fabricating the same and more particularly to a TFT and a method of fabricating the same, in which a fabrication process is simplified and the potential for damage to a gate insulating layer is decreased.
2. Discussion of Related Art
Recently, thin film transistors (TFT) have become widely used as switching devices that operate pixels in displays such as organic light emitting displays (OLED) and liquid crystal displays (LCD). Therefore, a great deal of attention has been focused on the design of effective TFTs and the fabrication of TFTs.
The process of fabricating conventional TFTs is described in detail with reference to the FIGS. 1 to 2F. FIG. 1 is a flowchart showing a process of fabricating conventional TFTs. FIGS. 2A to 2F are sectional views illustrating the process of fabricating the conventional TFTs of FIG. 1.
Referring to FIGS. 1 and 2A to 2F, to fabricate a conventional TFT 200, first, a substrate 201 is provided (block P1).
After the substrate 201 is provided, a buffer layer 202 is formed on the substrate 201. The buffer layer 202 is an optional component and may be formed of a single layer or a plurality of layers. A nitride layer or an oxide layer is used as the buffer layer 202. The buffer layer 202 of the TFT 200 illustrated in FIGS. 2A to 2F is composed of a first buffer layer 202a formed of a nitride layer and a second buffer layer 202b formed of an oxide layer (block P2).
After the buffer layer 202 is formed, an amorphous silicon layer a-Si is formed on the second buffer layer 202b. The formed amorphous silicon layer a-Si is crystallized by application of a laser. When the amorphous silicon layer a-Si is crystallized, the crystallized amorphous silicon layer a-Si is patterned to form a semiconductor layer 203 (block P3)
Referring to FIG. 2B, after the semiconductor layer 203 is formed, a gate insulating layer 204 is formed on the semiconductor layer 203. After the gate insulating layer 204 is formed, a mask 210 is formed. The mask 210 is formed on the gate insulating layer 204, covering a first region 203a of the semiconductor layer 203. Thus, the regions of the semiconductor layer 203b other than the first region 203a are doped using the mask 210. An n or p type dopant may be implanted. The doped semiconductor layer region 203b becomes source and drain regions and is referred to as a first doping region 203b (block P4). After the first doping region 203b is formed, the mask 210 is removed.
Referring to FIG. 2C, next, a metal layer (not shown) is formed on the gate insulating layer 204. The formed metal layer is patterned to form a gate electrode 205 (block P5).
After the gate electrode 205 is formed, a second doping region 203c is formed in the semiconductor layer 203 using the gate electrode 205 as a mask. The second doping region 203c is a lightly doped drain (LDD) region formed between the first doping region 203b and the first region or channel 203a of the semiconductor layer 203 (block P6).
Referring to FIG. 2D, after the second doping region 203c is formed, an interlayer insulating layer 206 is formed on the gate electrode 205 (block P7).
Referring to FIG. 2E, after the interlayer insulating layer 206 is formed, a plurality of contact holes 207 that expose the source and drain regions (i.e., the first doping regions 203b) are formed through the interlayer insulating layer 206 (block P8).
Referring to FIG. 2F, after the contact holes 207 are formed, source and drain electrodes 208 of the TFT 200 that are electrically connected to the first doping region 203b and are formed through the contact holes 207 (block P9).
The conventional TFT 200 is fabricated through the foregoing process (blocks P1 through P9). In this fabrication process (blocks P1 through P9), masks are needed for forming the first and second doping regions 203b and 203c, as a result the total fabrication process is complicated. Further, the gate insulating layer 204 may be damaged during the doping process, and a dopant may be non-uniformly distributed. Therefore, the TFT 200 may breakdown and the mobility may deteriorate.